For handicapped persons, mobility is greatly enhanced by the availability of vehicles having wheelchair lifts. Powered wheelchair lifts in which much or all of the movement of the wheelchair lift is motorized are particularly useful because of the inconvenience of physical activity by a person in a wheelchair. Many wheelchair lifts have been described in various patents. For example, U.S. Pat. No. 5,228,538 (Trembley) discloses a passenger lift suitable for use with a vehicle. The lift incorporates an electronic safety interlock to prevent all movement of the lift until a restraining belt is fastened. The lift has a pivotal mechanism for raising and lowering a platform. U.S. Pat. No. 5,261,779 (Goodrich) discloses a dual hydraulic, parallelogram arm wheelchair lift assembly for use in commercial vehicles. The lift assembly has a platform connected to a parallelogram linkage. In both of the above lift assemblies, when the platform of the lift is in a stowed position, the platform essentially blocks the doorway, making it very inconvenient to use the doorway in any other way.
Rotary wheelchair lifts that do not completely block the door when in a stowed position have been described. For example, U.S. Pat. No. 4,664,584 (Braun et al.) discloses a rotary wheelchair lift comprising a hydraulic lift having a vertically telescoping slide tube and a horizontal wheelchair platform support arm attached to the lower end of the slide tube. An in-out switch causes the platform to be rotated into or out of the vehicle around a vertical axis offset from, but parallel to, the slide tube. U.S. Pat. No. 5,180,275 (Czech et al.) discloses a rotary wheelchair lift that is retrofittable in transit vehicles. When stowed, the platform is nested against a transit seat and remains behind a closed door (behind half of a double-door pair). For use, the lift is deployed, rotated through the open double-door pair and lowered to the ground. The wheelchair lift has a variety of lockout switches and circuitry. However, in both of the rotatable wheelchair lifts, the platform, as well as the pivotal mechanism for deploying and moving the platform still take up a substantial amount of space.
U.S. Pat. No. 4,140,230 (Pearson) discloses a powered loading platform suitable for loading a wheelchair from the ground into the interior of a vehicle. The powered loading platform includes support means which pivotally support a horizontal platform and is carried by a powered parallelogram linkage. After loading the wheelchair into the vehicle, the platform can be collapsed and then pivoted to a vertically extending position entirely within the confines of the vehicle. However, even when collapsed, the powered platform still takes up a lot of room in the vehicle. Moreover, the horizontal position of the platform cannot be fine tuned to a desired position before it is lowered or raised between the vehicle and the ground. U.S. Pat. No. 4,353,436 (Rice et al.) also discloses a wheelchair lift having a foldable platform. The wheelchair lift also occupies much room even when stowed.
U.S. Pat. No. 5,234,331 (Loduha, Jr. et al.) discloses a wheelchair lift with adjustable post. The lift also has a pivotal end flap which rotates from a horizontal position during loading to an upright position during raising or lowering of the platform. This lift also blocks much of the doorway when in a stowed position.